Human rights activists have slammed the trial as a sham and accuse Russia of trying "revenge" against Safronov.
A Russian investigative journalist has been sentenced to 22 years in prison on charges of "high treason".
Ivan Safronov was found guilty of passing Russian military secrets to Czech intelligence. He has rejected the allegations.
Safronov worked as a journalist for a decade, covering military and security issues for the leading Russian business daily Kommersant, before becoming an adviser to the head of the Russian space corporation Roscosmos in May 2020.
He states that he has collected information from open sources in the course of his work and did nothing illegal. Roscosmos has also said that Safronov didn’t have access to state secrets and says that the charges didn’t relate to his work.
The former journalist had also rejected an offer from prosecutors to confess and receive a 12-year sentence.
Human rights activists have called for Safronov’s release, some claiming that Moscow may have wanted to silence him after his reporting exposed Russian military incidents and underhand arms deals.
Those accused of treason in Russia often find it difficult to defend themselves because of the secrecy surrounding their cases and a lack of public access to information.
Safronov’s father also worked for Kommersant covering military issues after retiring from the armed forces. In 2007, he died after falling from a window of his apartment building in Moscow.
Safronov's case reflects the growing challenges faced by Russian journalists amid Moscow’s invasion of Ukraine.
On Monday, a Russian court also revoked the licence of Novaya Gazeta, one of the last independent news outlets in the country.
The investigative newspaper had already suspended its operations amid threats if it shared so-called "fake news" about Russia's military.
Russia's state communications watchdog had accused the newspaper of failing to submit "the statutes of the editorial staff" under law.
"Today they killed the newspaper," a statement read. "They have robbed its employees of 30 years of their lives. They have deprived its readers of the right to information."
A spokeswoman for the Office of the High Commissioner for Human Rights also denounced the revoking as a "new blow" to the independence of the Russian media.
Novaya Gazeta has published investigations into corruption and human rights violations in Russia for nearly 30 years.
Several contributing journalists have been killed, including Anna Politkovskaya — whose assassination in October 2006 was linked to the Kremlin due to her investigative work on crimes committed in Chechnya.
Novaya Gazeta's editor-in-chief Dmitry Muratov also received the Nobel Peace Prize in 2021 for his work under threats from Moscow.
On Monday, Novaya Gazeta's editorial staff shared a letter of support for Safronov, labelling his arrest an act of "revenge".